Extra Torque Research Articles

Mechanisms modulating spinal excitability after nerve stimulation inducing extra torque

The study included three experiments aiming to examine the mechanisms responsible for spinal excitability modulation, as assessed by the H-reflex, following stimulation trains delivered at two different frequencies (20 and 100 Hz) inducing extra torque (ET). A first experiment (n = 15) was conducted to evaluate changes in presynaptic inhibition acting on Ia afferents induced by these electrical stimulation trains, assessed by conditioning the soleus H-reflex (tibial nerve stimulation) with stimulation of the common peroneal nerve (D1 inhibition) and of the femoral nerve (heteronymous Ia facilitation, HF). A second experiment (n = 12) permitted to investigate homosynaptic postactivation depression (HPAD) changes after the stimulation trains. A third experiment (n = 14) analyzed changes in motoneuron intrinsic properties after the stimulation trains, by electrically stimulating the descending corticospinal tract at the thoracic level, evoking thoracic motor-evoked potentials (TMEP). Main results showed that in all experiments, spinal excitability decreased after the 20-Hz train (P < 0.05), whereas this parameter significantly increased after the 100-Hz stimulation (P < 0.05). D1 and HF were not significantly modified after either stimulation. HPAD was significantly decreased only after the 20-Hz train, whereas TMEP was significantly increased only after the 100-Hz train (P < 0.05). It is concluded that the decreased spinal excitability observed after the 20-Hz train cannot be attributed to D1 presynaptic inhibition but rather to increased HPAD of the Ia afferents terminals, whereas the increase of this parameter obtained after the 100-Hz train can be assigned to changes in intrinsic motoneuron properties allowing to maintain Ia-α-motoneurons transmission efficacy.NEW & NOTEWORTHY Using different electrophysiological techniques, results show that the downregulation of spinal excitability observed after the 20-Hz train could be ascribed to homosynaptic postactivation depression of the Ia afferents terminals, whereas changes in intrinsic motoneuron properties could explain the increased spinal excitability observed after the 100-Hz train. A novel methodology for assessing soleus D1 presynaptic inhibition and heteronymous Ia facilitation, accounting for eventual modulations of test reflex amplitude throughout the session, was developed.

Influence of wide-pulse neuromuscular electrical stimulation frequency and superimposed tendon vibration on occurrence and magnitude of extra torque

Low-frequency and high-frequency wide-pulse neuromuscular electrical stimulation (NMES) can generate extra-torque (ET) via afferent pathways. Superimposing tendon vibration (TV) to NMES can increase the activation of these afferent pathways and favour ET generation. Knowledge of the characteristics of ET is essential to implement these stimulation paradigms in clinical practice. Thus, we aimed at investigating the effects of frequency and TV superimposition on the occurrence and magnitude of ET in response to wide-pulse NMES. NMES-induced isometric plantar flexion torque was recorded in 30 healthy individuals who performed five NMES protocols: wide-pulse low-frequency (1 ms; 20 Hz; WPLF) and wide-pulse high-frequency (1 ms; 100 Hz; WPHF) without and with superimposed TV (1 mm; 100 Hz) and conventional NMES (50 µs; 20 Hz; reference protocol). Each NMES protocol began with an adjustment of NMES intensity in order to reach 10% of maximal voluntary contraction then consisted of three 20-s trains interspersed by 90 s of rest. The ET occurrence was similar for WPLF and WPHF (p=0.822). In the responders, the ET magnitude was greater for WPHF than WPLF (p<0.001). There was no effect of superimposed TV on ET characteristics. This study reported an effect of NMES frequency on ET magnitude, whereas TV superimposition did not affect this parameter. In the context of our experimental design decisions, the present findings question the clinical use of wide-pulse NMES and its combination with superimposed TV. Yet, further research is needed in order to maximize force production through the occurrence and magnitude of ET.

Dynamics and phase-based vibration suppression of rotating flexible shaft with unstressed initial deformation under several parametric excitations

A rotating flexible cantilever shaft is modeled with unstressed initial deformation under several parametric excitations, including fluctuant speed, axial force, torque and nonlinear radial follower force. Its dynamics is calculated via an improved Hill's method which is suitable for harmonic processing. An iteration method for solving the steady-state response of the nonlinear system's dynamics is proposed, and the stability is determined by the perturbation of the steady-state response. Considering the effects of a single excitation and different excitations’ coupling, two criteria for evaluating the system's dynamics are investigated by numerical simulation. One is the eccentric degree of the shaft's rotating deformation, and the other is the stability of the shaft system. The excitations’ coupling effect provides a novel method, called the phase-based vibration suppression method in this paper, to suppress the rotating deformation of a shaft with fluctuant speed or radial follower force by applying an extra fluctuant axial force or torque. Meanwhile, this systematic method to solve the steady-state dynamics of the shaft is universal for practical engineering.

Novel DC-Saturation-Relieving Hybrid Reluctance Machine With Skewed Permanent Magnets for Electric Vehicle Propulsion

Reluctance machines with dc excitation coils have become a promising solution for electric vehicle propulsion system because of its robust rotor structure and good field-weakening ability. However, these machines usually suffer from relatively low torque density and efficiency. To solve this problem, this article proposes a novel hybrid reluctance machine with improved torque density and efficiency. The key novelty is to introduce skewed permanent magnets (PMs) in slot openings. The tangential component of skewed PMs can be used to relieve the dc saturation in the stator iron core, so that the <inline-formula> <tex-math notation="LaTeX">$B-H$ </tex-math></inline-formula> working range can be extended and relatively high dc excitation can be applied in the proposed machine. Besides, the radial component of skewed PM provides extra torque component under flux modulation effect. Therefore, the proposed skewed PMs can achieve torque boost and core utilization improvement simultaneously. In this article, the dc-saturation-relieving effect of the proposed design is thoroughly investigated and verified by finite element analysis.

Modulation of torque evoked by wide-pulse, high-frequency neuromuscular electrical stimulation and the potential implications for rehabilitation and training

The effectiveness of neuromuscular electrical stimulation (NMES) for rehabilitation is proportional to the evoked torque. The progressive increase in torque (extra torque) that may develop in response to low intensity wide-pulse high-frequency (WPHF) NMES holds great promise for rehabilitation as it overcomes the main limitation of NMES, namely discomfort. WPHF NMES extra torque is thought to result from reflexively recruited motor units at the spinal level. However, whether WPHF NMES evoked force can be modulated is unknown. Therefore, we examined the effect of two interventions known to change the state of spinal circuitry in opposite ways on evoked torque and motor unit recruitment by WPHF NMES. The interventions were high-frequency transcutaneous electrical nerve stimulation (TENS) and anodal transcutaneous spinal direct current stimulation (tsDCS). We show that TENS performed before a bout of WPHF NMES results in lower evoked torque (median change in torque time-integral: − 56%) indicating that WPHF NMES-evoked torque might be modulated. In contrast, the anodal tsDCS protocol used had no effect on any measured parameter. Our results demonstrate that WPHF NMES extra torque can be modulated and although the TENS intervention blunted extra torque production, the finding that central contribution to WPHF NMES-evoked torques can be modulated opens new avenues for designing interventions to enhance WPHF NMES.

Orientational dynamics of magnetotactic bacteria in Earth's magnetic field-a simulation study.

We investigate through simulations the phenomena of magnetoreception to enable an understanding of the minimum requirements of a fail-safe mechanism, operational at the cellular level, to sense a weak magnetic field at ambient temperature in a biologically active environment. To do this, we use magnetotactic bacteria (MTB) as our model system. The magnetic field sensing ability of these bacteria is due to the presence of magnetosomes, which are internal membrane-bound organelles that contain an iron-based magnetic mineral crystal. These magnetosomes are usually found arranged in a chain aligned with the long axis of the bacterial body. This arrangement yields an overall magnetic dipole moment to the bacterial cell. To simulate this orientation process, we set up a rotational Langevin stochastic differential equation and solve it repeatedly over appropriate time steps for isolated spherical shaped MTB as well as for a more realistic model of spheroidal MTB with flagella. The orientation process appears to depend on shape parameters with spheroidal MTB showing a slower response time compared to spherical MTB. Further, our simulation also reveals that the alignment to the external magnetic field is more robust for an MTB when compared to single magnetosome. For the simulation involving magnetosomes, we include an extra torque that arises from the twisting of an attachment tether and enhance the viscosity of the surrounding medium to mimic intracellular conditions in the governing Langevin equation. The response time of alignment is found to be substantially reduced when one includes a dipole interaction term with a neighboring magnetosome and the alignment becomes less robust with increase in inter dipole distance. The alignment process can thereby be said to be very sensitively dependent on the distance between magnetosomes. Simulating the process of alignment between two neighboring magnetosomes, both in the absence and presence of an ambient magnetic field, we conclude that alignment between these dipoles at the distances typical in an MTB is highly probable and it would be the locked unit that responds to changes in the external magnetic field.

Controllable Height Hopping of a Parallel Legged Robot

Legged robots imitating animals have become versatile and applicable in more application scenarios recent years. Most of their functions rely on powerful athletic abilities, which require the robots to have remarkable actuator capacities and controllable dynamic performance. In most experimental demonstrations, continuous hopping at a desired height is a basic required motion for legged robots to verify their athletic ability. However, recent legged robots have limited ability in balance of high torque output and actuator transparency and appropriate structure size at the same time. Therefore, in our research, we developed a parallel robot leg using a brushless direct current motor combined with a harmonic driver, without extra force or torque sensor feedback, which uses virtual model control (VMC) to realize active compliance on the leg, and a whole-leg control system with dynamics modeling and parameter optimization for continuous vertical hopping at a desired height. In our experiments, the robot was able to maintain stability during vertical hopping while following a variable reference height in various ground situations.

The Operational Space Formulation on Humanoids Considering Joint Stiffness and Bandwidth Limit

As the applications of robots increase, mobility and capability of interaction in unstructured environments have become important. Hence, humanoid robots have been developed to have these capabilities, and recently, compliant motions for safe contact have been studied. The Operational Space Formulation can be an effective method for humanoid robots to realize compliant motion via unified motion and force control. Nevertheless, the implementation of the Operational Space Formulation on humanoid robots has not been successful. One of the challenging issues is low position tracking performance. In this study, a control method for solving this problem is proposed by considering the joint stiffness and joint bandwidth limits. To consider joint stiffness, the Operational Space Formulation was derived using flexible joint robot dynamics. Additionally, an extra torque generation method, which penalizes low performance actuators, is utilized to account for the bandwidth limits. Neither methods requires additional sensors or joint space controllers. Hence, they can be useful for conventional humanoid robots composed of electric motors and gears. By integrating the two methods, the position tracking performance of the Operational Space Formulation on the humanoid robot was significantly improved. The proposed method was demonstrated via position and orientation control experiments using our humanoid robot, TOCABI.

Fuel enhancement of parallel hybrid electric two-wheeler motorcycle

In this paper, design and simulation of a parallel hybrid electric two-wheeler motorcycle (PHETM) by means of continuous variable transmission (CVT) is illustrated. For simulation, the parallel hybrid electric power train model type in MATLAB/ADVISOR is customized. The internal combustion engine (ICE) be supposed to drive at elevated efficiency areas, in order to attain enhanced fuel economy and a reduced amount of emission. Simultaneously, the ICE must not activate at values of low torque areas. For that reason, get better it whilst ICE is ON, a new energy control strategy is proposed. In the new strategy, the electrical machine absorbs the extra torque of the ICE. This article proposes a PHETM system to propel the vehicle efficiently with reduced amounts of emission on comparing witha conventional vehicle. This system includes two modes of operations for achieving the better results known as motoring mode and generating mode. The switching from one mode to other is based on the vehicle speed which is sensed in real time. A drive cycle is generated by running the vehicle in normal and slightly gradient condition and finally the results are compared.

Signal injection method without torque ripple for stator winding temperature estimation of surface-mounted PMSM drive systems

A signal injection method without torque ripple is presented to estimate the stator winding temperature of a surface-mounted permanent magnet synchronous machine (PMSM), where the temperature is estimated based on the stator resistance. First, the current signal (Δid*) is injected into the current control loop to produce DC current offsets used to calculate the stator resistance, where the injected signal cannot lead to extra torque ripple. Then the temperature can be obtained based on the relationship between the stator winding temperature and the stator resistance. Finally, the proposed method is validated by simulation and experimental results. In addition, no extra equipment is needed for the proposed method.

풍력터빈 축소모델 적용을 위한 3D 프린팅 블레이드 성능 실험

In this study, blades manufactured by 3D printing technology were experimentally tested to be used for a scaled wind turbine in a wind tunnel. The scaled model was originally designed and manufactured by researchers at the Technical University of Munich. The model has been slightly modified to adopt the 3D printed blades for this study. Also, control algorithms for the power maximization in the low wind speed regions were constructed and applied to a commercial programmable logic controller for wind tunnel tests of the scaled model. For comparison, the scaled model was also modeled in MATLAB/Simulink and dynamic simulations were performed with the measured wind speed as an input. The simulation results seemed to overpredict the experimental results initially, but by considering the unexpected extra generator torque due to friction of the shaft, the errors were reduced to be less than 5%. Based on this study, the application of 3D printed blades to the wind turbine scaled models of a similar rotor diameter was found to be an efficient and effective way of blade manufacturing and scaled model testing.

Flux-Modulated Relieving-DC-Saturation Hybrid Reluctance Machine With Synthetic Slot-PM Excitation for Electric Vehicle In-Wheel Propulsion

The reluctance machine with dc field coils in stator is an emerging brushless candidate for the in-wheel direct drive for its wide speed range and robust mechanical structure, while it suffers from relatively low torque density and efficiency, due to the poor excitation ability of dc field coils and worse extra dc saturation effect in the stator core. To address this issue, a new hybrid reluctance machine is proposed in this article, in which an integrated dual-layer PM source is introduced into stator slots, aiming to relieve dc saturation and, meanwhile, evoke flux modulation effect. In this way, the stator core utilization factor can be boosted due to dc saturation elimination by inner-layer slot permanent magnets (PM). On the other side, extra PM torque is generated by the flux modulation effect of outer-layer slot PMs. Hence, with synthetic assistance from dual-layer slot PMs, the torque density is improved distinctly especially under relatively high current density. Besides, slot PMs share a parallel magnetic circuit with dc field coils, which enables a bidirectional dc magnetization control for speed range extension. In this article, the proposed new topology is fully evaluated by both finite element (FE) analysis and prototype experiments.

Compound pendulum pivot force

The force at the pivot of a simple pendulum and the acceleration of the bob have been the subject of a number of papers. The present paper extends this analysis to a compound pendulum, which requires an extra torque to rotate the pendulum about its center of mass. The dependence of the pivot force on κ = k/a, the ratio of the radius of gyration k to the center of mass position a, is investigated. The pivot force on an ideal compound pendulum is shown to be the same as that for a lighter simple pendulum plus a mass located at the pivot.

Impact of stimulation frequency on neuromuscular fatigue.

The aim of the present study was to examine the frequency effects (20Hz and 100Hz) on neuromuscular fatigue using stimulation parameters favoring an indirect motor unit recruitment through the afferent pathway. Nineteen subjects were divided into two groups: 20Hz (n = 10) and 100Hz (n = 9). The electrical stimulation session consisted of 25 stimulation trains (20s ON/20s OFF, pulse width: 1ms) applied over the tibial nerve and delivered at an intensity evoking 10% maximal voluntary isometric contraction (MVIC). Before and after these protocols, MVIC was assessed, while neural changes were evaluated by the level of activation (VAL) and muscle changes were evaluated by the twitch associated with the maximal M-wave (Pt). For all stimulation trains, the real and the theoretical values of the torque-time integral (TTIr and TTIth, respectively) were calculated. The TTIr/TTIth ratio of the first train was calculated to evaluate the presence of extra torque. The main results showed a similar decrease in MVIC torque after both protocols accompanied by neural and muscle changes, as evidenced by the decrease in VAL and Pt. TTIr values across the 20-Hz trains remained constant, whereas they significantly decreased during the 100-Hz stimulation trains. The relative MVIC decrease was negatively correlated with TTIr/TTIth. Results give evidence of an identical neuromuscular fatigue development between protocols, while lower stimulation frequency permitted preservation of a given torque level during the stimulation trains. The negative correlation between this fatigue development and TTIr/TTIth suggests that extra torque production induces greater voluntary torque losses.

Tilting‐Sensitive Triboelectric Nanogenerators for Energy Harvesting from Unstable/Fluctuating Surfaces

AbstractThe invention of triboelectric nanogenerators provides an opportunity to utilize previously wasted mechanical energy. The sway energy of ships that affects navigation and comfort on board has been considered negative in the past. Here, a tilting‐sensitive triboelectric nanogenerator (TS‐TENG) that can effectively harvest energy from unstable/fluctuating surfaces is demonstrated by using the sway energy of ships. The device adopts integrated blade structures on sliders, which make it sensitive to tilts and guarantee its power output. The response of the device to tilt agitations of different slopes and frequencies is systematically investigated. Rotational symmetry configuration is used to improve the motion stability of the device by excluding extra torque on the sliders. The peak power density and average power density of the TS‐TENG can reach 1.41 and 0.1 W m−3, respectively, in low‐frequency and low‐amplitude fluctuating conditions. By the excellent performance of harvesting energy from unstable/fluctuating surfaces, the TS‐TENG is considered promising for powering various distributed sensor devices on the ship for smart ships.

Finite element analysis of the effect of power arm locations on tooth movement in extraction space closure with miniscrew anchorage in customized lingual orthodontic treatment.

More patients are choosing customized orthodontic appliances because of their excellent esthetics. It is essential that clinicians understand the biomechanics of the tooth movement tendency in customized lingual orthodontics. This study aimed to evaluate the tooth movement tendency during space closure in maxillary anterior teeth with the use of miniscrew anchorage in customized lingual orthodontics with various power arm locations. Three-dimensional finite element models of the maxilla were created with miniscrews and power arms; the positions were varied to change the force directions. A retraction force (1.5N) was applied from the top of the miniscrews to the selected points on the power arm, and the initial displacements of the reference nodes of the maxillary teeth were analyzed. After applying force in different directions, power arms located at the distal side of the canines led to larger initial lingual crown tipping and occlusal crown extrusion of the maxillary incisors compared with power arms located at the midpoint between the lateral incisors and canines, and caused a decreasing trend of the intercanine width. In customized lingual orthodontic treatment, power arms located at the distal side of the canines are unfavorable for anterior teeth torque control and intercanine width control. Power arms located at the midpoint between the lateral incisors and canines can get better torque control, but still cannot achieve excepted torque without extra torque control methods, no matter whether its force application point is higher than, lower than, or equal to the level of the top of the miniscrews.

Multiple Reference Frame Based Torque Ripple Minimization for PMSM Drive Under Both Steady-State and Transient Conditions

Torque ripple has been a critical issue for high-performance applications using permanent magnet synchronous machines (PMSMs). An efficient approach to minimize torque ripple is to control the stator current to follow an optimized current reference, which will produce an extra torque ripple to cancel the existing one. This paper proposes a multiple reference frame (MRF) based controller for torque ripple minimization (TRM), in which the measured speed ripple is explored as the feedback control signal. The proposed MRF-based controller consists of a TRM controller whose task is to find the optimal current reference and a current controller whose task is to control the actual current to follow the optimized current reference. In TRM controller, the control of reference current magnitude and phase angle is decoupled, and proportional integral (PI) controller is able to achieve TRM control. In current controller, MRF is adopted to convert harmonic current control into dc current control; thus, PI controller is able to achieve harmonic current control with the use of MRF. Compared with existing approaches, the proposed controller is capable of TRM under both steady-state and transient conditions. The proposed controller is experimentally evaluated on a laboratory PMSM drive system.

Tightening behavior of bolted joint with non-parallel bearing surface

Non-parallel bearing surface resulting from accumulation of geometric deviations is often unavoidable in tightening process of bolted joint, which has a significant influence on the tightening accuracy. In this study, the mechanism of preload deviation caused by non-parallel bearing surface is proposed by analytical model. Then the tightening behaviors of non-parallel bolted joint with different geometric parameters are analyzed through parametric FEA. Finally, the bolt tightening experiment is carried out, which verified the theoretical hypothesis and the FEA model. The results show that the extra thread friction torque generated by lateral pressing in mating threads resulting from bending moment is the cause of preload deviation. Larger inclination angle of bearing surface, shorter grip length of bolted joint and smaller fitting clearance between internal and external threads will increase this preload deviation.

Non Integer Order Modeling and Control of Aerodynamic Load Simulator System

This article investigates the non-integer order model and the controller for aerodynamic load simulator system using fractional order adaptive fuzzy back stepping method. Extra torque disturbance is analyzed using fractional mathematics and a non-integer state predictor is proposed for the estimation of the state vector. For the lumped uncertainty, a fractional order compensation control is formulated using Lyapunov method. Algebraic estimator is derived to estimate the unknown parameters of the system. The proposed controller is simpler in structure and robust to noise, initial conditions. Simulation results authenticate the performance of the proposed control method.

Development of Efficiency Enhanced Scotch Yoke Mechanism for Robotic Fish

A Scotch yoke mechanism can provide high thrust by generating high frequency flapping motion in a propulsion system of robotic fish. However, higher frequency makes higher drag force, and if the motor torque is insufficient compared to the drag force, this causes a lagging phenomenon due to the lack of torque, which causes a problem of lowering the thrust. In this paper, we propose an efficiency enhanced scotch yoke mechanism through output torque re-distribution. We focus on the fact that the required motor torque of the Scotch yoke mechanism is not constant in the fin propulsion system; thus, it is not necessary to raise the torque in the entire domain. By transferring the extra torque in a certain section to the torque-insufficient section, the frequency and thrust can be increased without increasing the motor size and energy consumption. We present a dynamic model and a design method of the proposed concept, and also validate the performance enhancement by comparing the thrust, frequency, and the period of the tail fin movement of conventional and enhanced system while the equal input current is supplied.